This invention relates generally to light fixtures, and, more particularly, to light fixtures for converting incandescent light fixtures for operation with light sources of another type, such as fluorescent.
In recent years, the cost of electrical energy has increased substantially, and a number of devices have become available for conveniently replacing incandescent lamps with types that are more efficient, such as fluorescent lamps. Typically, these devices have a standard screw fitting for connection to an incandescent lamp socket, and include one or more flourescent tubes, often shaped in a circular pattern, together with the components necessary to operate the fluorescent lamp, such as a transformer or ballast.
One type of incandescent fixture that is commonly converted for fluorescent operation is the recessed ceiling fixture. Basically, this fixture comprises a generally cylindrical or square housing recessed into the ceiling, and a conventional incandescent screw socket fitting positioned at the top of the housing to receive an incandescent bulb. Recessed fixtures of this type may be supplied in a wide range of sizes, and this variation makes adaptation for fluorescent operation extremely difficult, since a fluorescent tube must usually be accommodated beneath the ceiling level, at varying lengths from the screw socket. Accordingly, devices of varying lengths must be manufactured and maintained in inventory in order to accommodate recessed fixture housings of various sizes.
One attempt to solve this problem is exemplified in U.S. Pat. No. 4,093,974, issued in the name of Wheeler, in which a fluorescent light is mounted at the end of a telescopically extensible member comprising two tubes of square cross section. At the other end of the telescopically extensible member is a standard screw fitting for connection to an incandescent light fixture, and the length of the extensible member is first adjusted to a selected length, and then maintained at that length by means of a spring disposed between the two telescoping tubes. Unfortunately, this structure has not proved entirely satisfactory, principally because a power-frequency hum associated with most fluorescent devices tends to set up vibration in the fixture. The fluorescent light is often vibrated downwardly over a period of time, until the extensible member is fully extended, leaving the light projecting down from the ceiling. In addition, the vibration may have the effect of slowly unscrewing the standard incandescent screw fitting, especially if it is not first properly tightened. Accordingly, there has, prior to this invention, been a need for an improved light fixture for converting incandescent light fittings for operation with lights of other types, and for providing a fixture of conveniently adjustable length, for installation in existing fixture housings of various sizes. The present invention fulfills this need.